JPH0436812B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an automatic screw tightening machine configured to reciprocate a driver bit that rotates in response to rotation of a rotational drive source by the operation of an elevating means. The present invention relates to a screw seating detection device for detecting seating of a screw.

PRIOR ART AND PROBLEMS TO BE SOLVED BY THE INVENTION Generally, when tightening screws, bolts, etc. to predetermined positions on a workpiece, an automatic screw tightening machine that has a driver bit that rotates in response to rotation of a motor is used. . In this automatic screw tightening machine, various control devices have been devised to control the motor in order to control the final tightening torque to a predetermined value. An example of this control device is a device that detects the load current of a motor and stops the rotation of the motor when the current value reaches a predetermined value. With this device, when inserting a screw into a prepared hole with a female thread, the tightening torque can be controlled to approximately a predetermined value. The load current of the motor may reach the set value or higher at the point where the motor stops and the tightening work is stopped midway, causing disadvantages such as not being able to perform the specified tightening work. There is. In order to eliminate this drawback, a method has been considered in which the height of the driver bit is detected to detect the point in time when the screw seating surface is seated on the seating surface of the workpiece, and the motor control device is activated after this point. However, even with this device, there are drawbacks such as the inability to accurately detect the seating of the screw and the inability to perform reliable tightening. In addition, a method for detecting when the screw is seated is to constantly detect the increase in the load current flowing through the motor per unit time when tightening the screw, that is, the slope, and if the slope falls within a predetermined range, the screw is seated. A method has been considered that determines that the screw is seated based on the increase in the load current after seating, but this method accurately detects changes even in the presence of noise contained in the load current, resulting in extremely erroneous operation. Therefore, there is a need for a screw seating detection device that is accurate and does not malfunction.

Means for Solving the Problems The present invention was developed in response to the above-mentioned needs, and is provided with a driver bit that rotates in response to rotation of a motor, and a lifting means for raising and lowering the driver bit. Further, a detection means for detecting the load torque related to the driver bit is provided. Together with the detection means, a first setting device sets a first setting value corresponding to the tightening torque at the start of tightening, and a second setting device corresponds to a tightening torque lower than the desired tightening torque.
A second setting device is provided for setting a set value.
Further, a first comparator that compares the detected value of the detection means and the first set value, and a second comparator that compares the detected value and the second set value are provided. Furthermore, a fourth timer in which a minimum tightening time is set and a fifth timer in which an upper limit tightening time is set are provided. , is configured to be reset as soon as the detected value falls below a first set value. Moreover, a seating determination section is provided which transmits an output signal if it receives a coincidence signal from the second comparator between the time-up of the fourth timer and the time-up of the fifth timer, and the output signal of the seating determination section is It is configured to arbitrarily control the motor in response to the

Function In the automatic screw tightening machine described above, when the motor rotates and tightening is started, the load torque related to the driver bit is detected by the detection means. When this detected value reaches the first set value indicating the time to start tightening, a coincidence signal is transmitted from the first comparator, and the fourth and fifth timers count the time. When a coincidence signal is transmitted from the second comparator within the lower limit tightening time and upper limit tightening time set by each of the timers, the rising slope of the detected value becomes a predetermined value indicating an increase in the tightening torque after the screw is seated. It is determined that the slope is within the slope range, and an output signal is transmitted from the seating determination section. The motor can then be controlled to stop it or change its speed as needed.

On the other hand, if a coincidence signal is not transmitted from the second comparator within the predetermined time, the rising slope of the detected value is not within the predetermined slope range indicating the rise in tightening torque after the screw is seated, and the pilot hole is The seating determination section stops accepting the coincidence signal from the second comparator due to the time-up signal of the fifth timer, determining that the detected value increases when forming the screw, and then the second comparator transmits the coincidence signal. Also, the seating determination section does not transmit an output signal. At this time, the fourth timer and the fifth timer
The timer continues to emit a time-up signal for a while, and when the detected value becomes lower than the first set value, it is reset, and the true screw seating is determined by the matching signals from the first and second comparators. Prepare for detection.

Embodiment Hereinafter, an embodiment will be described regarding an automatic screw tightening machine having a driver bit that receives rotation of a motor via a speed reducer using a differential planetary mechanism. Second
In the figures and FIG. 3, reference numeral 1 denotes an automatic screw tightening machine, and a driver stand 4 is integrated with a guide rod 3 that is slidably guided in the vertical direction by a bracket 2.
is disposed at a predetermined distance from the desk 5 so as to be movable integrally with and relative to the desk. The driver stand 4 is configured to be raised and lowered by the operation of a cylinder constituting an elevating means 6, and a driver main body 8 is fixed to the driver stand 4. A motor 9 as a rotational drive source is fixed to the upper end of the driver main body 8, and a differential planetary mechanism 1 is attached to the drive shaft of the motor 9.
An input disk 11 constituting a part of 0 is connected so as to rotate together. Also, this input disk 1
A plurality of planetary cones 12 are arranged on the outer periphery of the cone 1 via a cone holder 13, and the planetary cones 12 are located adjacent to a conical surface 12a and a flat surface 12b on the back surface as transmission surfaces. Circumferential groove 1
2c is formed. The input disk 11 is placed in the circumferential groove 12c of the planetary cone 12, and the flat surface 1
2b, a cam disk 14 that rotates concentrically with the input disk 11 is arranged so as to frictionally engage with the input disk 11.
4. The cam disk 14 is connected to the driver via a connecting shaft 15, a connecting mechanism 16, and a universal joint 17, which are fixed to the driver base 4 and rotatably held in an inner cylinder portion 8a located inside the driver main body 8. Bit 18 is concatenated. The connecting mechanism 16
has a shaft portion 16a connected to the cam disk 14 side and a cylindrical portion 16b into which this fits, and the shaft portion 16a
The pin 16c implanted in the shaft part 16 engages with the guide groove 16d cut in the cylindrical part 16b.
a and the cylindrical portion 16b are urged in the direction of separation by a spring 16e, and are configured to be integrally rotatable and relatively movable.

Further, a speed change ring 19 is arranged on the outer periphery of the planetary cone 12 so as to rotate by frictionally engaging with the conical surface 12a thereof, and this speed change ring 19 is arranged so that its frictional engagement position is located on the high speed side. is biased by a spring 20. Further, this speed change ring 19 is rotatably held by an arm 21 rotatably held on the inner cylinder portion 8a side,
The elastic holding member consisting of the arm 21 and the spring 20 is configured to determine the frictional engagement position of the speed change ring 19. Further, in the differential planetary mechanism 10, the speed change ring 19 rotates in response to load torque, and the pressing force on the spring 20 and the spring 20
The rotation of the input disk 11 is decelerated and transmitted to the cam disk 14, and finally the speed change ring 19 moves to the edge of the planetary cone 12 and the rotation of the input disk 11 is transmitted to the cam disk 14. 14
is configured to reach zero rotation and output a tightening torque as shown in the characteristic curve shown in FIG.

Further, a chuck unit 22 having a pair of chuck pawls 22a is fixed to the chuck base 5, and the driver bit 18 is inserted into the chuck unit 22 to screw a screw (not shown) held by the chuck pawls 22a. It is configured to be pushed out to a predetermined position.

On the other hand, the motor 9 is configured to be controlled by a control device A. This control device A is
As shown in FIG. 1, a normal rotation voltage supply section 40 that supplies a forward rotation voltage to the motor 9, a reverse rotation voltage supply section 41 that supplies a reverse rotation voltage, and a normal rotation voltage supply section 40 and a reverse rotation voltage supply section 41. A switching means 42 for switching, a forward rotation control section 43 that provides a forward rotation command signal to the switching means 42, and a reverse rotation control section 44 that provides a reverse rotation command signal.
, a work start section 45 that issues a work start signal, a tightening completion detection section 46 that detects the completion of screw tightening by the driver bit 18, a tightening defect determination section 61 (to be described later), and a first timer T1. It has a reset section 57 for resetting. The normal rotation control section 43 is a pulse generation section that emits a high pulse train, and is configured to operate a switching section constituting the switching means 42 to supply a normal rotation voltage to the motor 9. Further, the work start section 45 is connected to the forward rotation control section 43 and the lifting means 6, and operates the forward rotation control section 43 and the lifting means 6 in response to the work start signal. is configured to lower. Further, the work start signal is configured to reset a determination display section 47 and a seating determination section 48, which will be described later, and to cause a first timer T1 for detecting machine time to count the time. Further, the switching means 42 is configured to receive a reverse rotation command signal from a reverse rotation control section 44, actuate the switching section, and supply a reverse rotation voltage from the reverse rotation voltage supply section 41 to the motor 9. The reverse rotation control section 44 is configured to transmit a reverse rotation command signal in response to a pulse from a pulse generator 59 which is activated in response to a time-up signal from a second timer T2, which will be described later.

Further, the tightening completion detection section 46 includes a torque detection section 50 and a screw seating detection device 51. The torque detection section 50 has a detection means 52 that detects a voltage corresponding to the load current flowing in the armature winding of the motor 9, and this detection means 52 is connected to a screw seating detection device via a filter 53 and an amplifier 54. It is connected to one input terminal of a second comparator 60 which also serves as a part of the comparator 51. This second comparator 6
A second setter 58 is connected to the other input of 0 to set a second setting value corresponding to a tightening torque lower than the desired tightening torque, and when the detected value matches this second setting value, , the matching signal is configured to be emitted. This second comparator 60 is connected to a third timer T3 via a seating determination section 48, and when this seating determination section 48 is activated, the third timer T3 receives a coincidence signal from the second comparator 60. The device is configured to transmit a time-up signal after a predetermined time (T3). Furthermore, the torque detection section 5
0 uses the second comparator 60 and second setting device 58 of the screw seating detection device 51 to detect that the detected value has reached a predetermined value, but a separate comparator and setting device are provided. Good too.

Further, the time-up signal of the third timer T3 is supplied to the forward rotation control section 43 via the OR circuit as a torque-up signal of the tightening completion detection section 46, and is configured to supply a forward rotation stop command signal to the switching means 42. It is composed of At the same time, the time-up signal of the third timer T3 is supplied to the pulse generator 59 via the second timer T2, which is set to the time (T2) required for the normally rotating motor 9 to stop. ing. This pulse generating section 59 is configured to generate a pulse having a pulse width corresponding to a desired reversal time, and this pulse is sent to the reversal control section 44, and a reversal command is issued according to the pulse width of this pulse. It is configured to send a signal to slightly reverse the motor 9. Further, the time-up signal of the second timer T2 is configured to actuate the lifting means 6 of the driver bit 18 via the machine cycle completion detecting section 49, so that the driver bit 18 is raised and returned to complete the entire work. There is.

Further, the screw seating detection device 51 includes a second setting device 58 that also serves as a part of the torque detection section 50;
A second comparator 6 that compares the second set value and the detected value.
0, a first setter 56 that sets a first set value corresponding to the tightening torque at the time of starting tightening, and a first comparator 55 that compares the first set value with the detected value.
The coincidence signal of the first comparator 55 is detected by a fourth timer in which a minimum tightening time is set.
5th timer with T4 and upper limit tightening time set
Configured to operate T5. Also,
The seating determination section 48 is configured to receive a coincidence signal transmitted from the second comparator 60 within the time set by the fourth timer T4 and the fifth timer T5 and transmit an output signal. On the other hand, the fourth
The timer T4 sends the time-up signal to the tightening defect determination section 61, and if a coincidence signal is sent from the second comparator 60 before this time-up signal,
It is configured to supply a poor tightening signal to the determination display section 47. Incidentally, the judgment display section 47 is also configured to receive a time-up signal from the first timer T1 and display a machine time-over. Furthermore, the fifth timer T5 uses the time-up signal to cause the seating determination section 48 to output the second comparator 60.
When the detected value falls below the first set value and no match signal is transmitted from the first comparator 55, the fifth timer
T5 is reset together with the fourth timer T4, and is configured to prepare for the coincidence signal sent from the first comparator 55 again. Furthermore, the fourth timer T4
The set time of the fifth timer T5 is empirically selected from the time obtained by actually tightening the screw to the workpiece.

In the control device for the automatic screw tightening machine described above, the lifting means 6 for the driver bit 18 is operated in response to a work start signal from the work start section 45, and the driver bit 18 is lowered together with the driver stand 4. at the same time,
The work start signal activates the forward rotation control section 43 and the switching means 42, and the forward rotation voltage is supplied to the motor 9 from the forward rotation voltage supply section 40. As the motor 9 rotates, the input disk 11 and the planetary cone 1
2. Driver bit 18 via differential planetary mechanism 10 consisting of cam disc 14 and speed change ring 19
rotates. The operation of the elevating means 6 causes the driver bit 18 to push out the screw held by the chuck pawl 22a, and its tip abuts against a prepared hole in a workpiece (not shown). Along with this, the connecting mechanism 16
Screw tightening is started while the shaft portion 16a moves forward with respect to the cylindrical portion 16b. (See Figure 5 below)
As the load torque related to the driver bit 18 increases, the load current of the motor 9 increases, and when the detected value reaches the first set value corresponding to the tightening torque indicating the tightening start time, the first comparator 55 A coincidence signal is sent from the fourth timer T4 and the fifth timer T5 count the time. The detected value is the fourth timer T4
When the second set value corresponding to the desired tightening torque is reached at the time when the time-up signal is emitted from the second comparator 60, a match signal is emitted from the second comparator 60. In this case, since the seating determination section 48 is in a state where it cannot accept the coincidence signal from the second comparator 60, no output signal is transmitted from the seating determination section 48, and the rising slope of the detected value is too steep, causing the screw It is determined that diagonal chamfering occurs, a defect detection signal is transmitted from the tightening defect determination section 61, and a defect is displayed on the determination display section 47.

Further, after the fourth timer T4 sends a time-up signal and puts the seating determination section 48 into an input acceptance state, the detected value reaches the second set value within the upper limit tightening time set in the fifth timer T5. When the fifth timer T5 times up, the seating determination section 48 no longer accepts the coincidence signal from the second comparator 60. Even if the second comparator 60 subsequently transmits a coincidence signal, the seating determination section 48 An output signal is not transmitted, and based on the gradual increase in the detected value, it is determined that the detected value has increased during female thread forming. Therefore, the motor 9 continues to rotate.

When the motor 9 continues to rotate and reaches the point where the forming of the female thread is completed, the detected value becomes lower than the first set value and the fifth timer T5 is reset together with the fourth timer T4. This results in
Prepare again for a match signal from the first comparator 55.

Thereafter, when the detected value increases and reaches the first set value, the fourth timer T4 and the fifth timer T5 start counting time again. When the detected value reaches the second set value within the tightening upper limit time from the lower limit tightening time, the rising slope of the detected value falls within a predetermined slope range indicating an increase in the tightening torque after the screw is seated normally. It is determined that the screw is seated on the seat surface. Therefore, at the time when a coincidence signal is transmitted from the second comparator 60 which also serves as the torque detection section 50,
The seating determination unit 48 transmits an output signal. This output signal causes the third timer T3 to start counting time.
The time-up signal is sent as a torque-up signal to the normal rotation control section 43, a normal rotation stop command signal is sent, and the motor 9 is stopped. At the same time, the time-up signal is sent to the second timer T2, and the second timer T2 counts the time. After the time (T2) required for the motor 9 to stop has elapsed, this second
The pulse generator 59 is actuated by the time-up signal transmitted from the timer T2, and generates a pulse for setting a predetermined reversal time. This pulse activates the reverse rotation control unit 44 to switch the switching means 42 to the reverse side, and a short pulse corresponding to the pulse is transmitted, and a reverse rotation voltage is supplied to the motor 9 from the reverse voltage supply unit 41. As a result, the motor 9
rotates slightly in the opposite direction, the load on the driver bit 18 is reduced from the motor 9 side, and the speed change ring 19
gradually returns along the planetary cone 12, and the differential planetary mechanism 10 and driver bit 18 are released from the locked state. Further, the time-up signal is supplied to the machine cycle completion detection section 49, and its output signal is supplied to the lifting means 6, which operates to raise the driver bit 18 in preparation for the next work.

Effects of the Invention As explained above, the present invention includes a detection means for detecting the load torque related to the driver bit, two comparators for comparing with two types of set values, and two comparators for setting the time within a predetermined range. It is configured to determine the rising slope of the detected value when tightening a screw and send an output signal when it is within a predetermined range, thereby reducing the complicated tightening torque when tightening a tatsu pin screw. Not only can screw seating be reliably detected even when changes in If so, there are advantages such as being able to provide a screw seating detection device that is automatically reset and is unlikely to malfunction.

In addition, although the embodiment performs on/off control of one motor, two motors are arranged, one for tightening until the screw is seated, and the other for tightening after the screw is seated. It is also possible to perform on/off control.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the present invention, Fig. 2 is an overall view of the present invention, Fig. 3 is a sectional view of essential parts of an automatic screw tightening machine according to the present invention, and Fig. 4 is a diagram of an automatic transmission according to the present invention. Torque-speed characteristic curve diagram of the output shaft,
FIG. 5 is a flowchart explaining the operation of the present invention. 1...Automatic screw tightening machine, 2...Bracket, 3
. . . Guide rod, 4 . ...Input disk, 12... Planetary cone, 12a... Conical surface, 12b... Flat surface, 1
2c... Circumferential groove, 13... Cone holder, 14...
...Cam disc, 15...Connection shaft, 16...Connection mechanism, 16a...Shaft part, 16b...Cylinder part, 16c
...Pin, 16d...Guide groove, 16e...Spring,
17... Universal joint, 18... Driver bit, 19... Speed change ring, 20... Spring, 21... Arm, 22... Chuck unit, 22a... Chuck pawl, A... Control device, 4
0...Forward rotation voltage supply section, 41...Reverse rotation voltage supply section, 42...Switching means, 43...Forward rotation control section, 4
4... Reverse control section, 45... Work start section, 4
6...Tightening completion detection section, 47...Judgment display section, 4
8...Setting determination section, 49...Machine cycle completion detection section, 50...Torque detection section, 51...Screw seating detection device, 52...Detection means, 53...Filter, 54...Amplifier, 55... first comparator, 56
...First setting device, 57...Reset section, 58...
Second setting device, 59...Pulse generation section, 60...Second comparator, 61...Tightening defect determination section.

Claims (1)

[Scope of Claims] 1. An automatic screw tightening machine configured to raise and lower a driver bit that rotates in response to the rotation of a motor using a lifting means, which is provided with a detection means for detecting a load torque related to the driver bit, a first setting device for setting a first setting value corresponding to a tightening torque at a starting point; a second setting device for setting a second setting value corresponding to a tightening torque lower than a desired tightening torque; the first setting device; A first comparator that compares the first set value of the setting device with the detected value and a second comparator that compares the second set value and the detected value are provided, and a second comparator that compares the first set value of the setting device with the detected value, and further includes a second comparator that compares the first set value of the setting device with the detected value. A fourth timer and a fifth timer having a tightening upper limit time set are provided, and the coincidence signal of the first comparator causes the fourth timer and the fifth timer to start counting the time, so that the detected value is lower than the first set value. When the timer decreases, the fourth timer and the fifth timer
The seating determination unit is configured to reset the timer, and further includes a seating determination unit that transmits an output signal when it receives a coincidence signal from the second comparator between the time-up of the fourth timer and the time-up of the fifth timer. Screw seating detection device.